Re: [PATCH 14/16] virtio-net: support queue_enable for vhost-user

[Jason Wang]

在 2022/7/18 19:17, Kangjie Xu 写道:
Support queue enable in vhost-user scenario. It will be called when
a vq reset operation is performed and the vq will be restared.

It should be noted that we can restart the vq when the vhost has
already started. When launching a new vhost-user device, the vhost
is not started and all vqs are not initalized until
VIRTIO_PCI_COMMON_STATUS is written. Thus, we should use vhost_started
to differentiate the two cases: vq reset and device start.

Signed-off-by: Kangjie Xu <kangjie...@linux.alibaba.com>
Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
---
  hw/net/virtio-net.c | 20 ++++++++++++++++++++
  1 file changed, 20 insertions(+)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 8396e21a67..2c26e2ef73 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -544,6 +544,25 @@ static void virtio_net_queue_reset(VirtIODevice *vdev, 
uint32_t queue_index)
      assert(!virtio_net_get_subqueue(nc)->async_tx.elem);
  }
  
+static void virtio_net_queue_enable(VirtIODevice *vdev, uint32_t queue_index)
+{
+    VirtIONet *n = VIRTIO_NET(vdev);
+    NetClientState *nc = qemu_get_subqueue(n->nic, vq2q(queue_index));
+    int r;
+
+    if (!nc->peer || !vdev->vhost_started) {
+        return;
+    }
+
+    if (nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_USER) {
+        r = vhost_virtqueue_restart(vdev, nc, queue_index);
+        if (r < 0) {
+            error_report("unable to restart vhost net virtqueue: %d, "
+                            "when resetting the queue", queue_index);
+        }
+    }
+}


So we don't check queue_enable in vhost_dev_start(), does this mean the 
queue_enable is actually meaningless (since the virtqueue is already 
started there)?

And another issue is

peet_attach/peer_detach() "abuse" vhost_set_vring_enable(). This 
probably means we need to invent new type of request instead of re-using 
VHOST_USER_SET_VRING_ENABLE.

Thanks


+
  static void virtio_net_reset(VirtIODevice *vdev)
  {
      VirtIONet *n = VIRTIO_NET(vdev);
@@ -3781,6 +3800,7 @@ static void virtio_net_class_init(ObjectClass *klass, 
void *data)
      vdc->bad_features = virtio_net_bad_features;
      vdc->reset = virtio_net_reset;
      vdc->queue_reset = virtio_net_queue_reset;
+    vdc->queue_enable = virtio_net_queue_enable;
      vdc->set_status = virtio_net_set_status;
      vdc->guest_notifier_mask = virtio_net_guest_notifier_mask;
      vdc->guest_notifier_pending = virtio_net_guest_notifier_pending;